Copyright © American Speech-Language-Hearing Association From: Long-Term Phonatory Instability in Individuals With Multiple Sclerosis J Speech Lang Hear Res. 1997;40(5):1056-1072. doi:10.1044/jslhr.4005.1056 Legend: Sample spectral analysis of phonatory data. The top panels depict an analysis of intensity and the bottom panels depict an analysis of fundamental frequency. Each set displays time-series data extracted from the last 2.56 seconds of a single phonation produced by a speaker with MS and the low frequency region of an FFT transform of those data. Date of download: 11/11/2017 Copyright © American Speech-Language-Hearing Association